The present invention is directed to a wound package of tape, and more particularly, to a step-wound package of tape and method and apparatus for making the same.
For many years, tape was wound onto a flat bank or cylindrical core in a single spiral where one layer or turn of tape lies directly on top of the previous layer or turn. Dependent upon the width of the tape and slipperiness of the material from which the tape is formed, the amount of tape that can be wrapped in such a single spiral is limited, as the greater the amount of tape, the less stable the package formed therefrom.
To increase the amount of tape that can be wrapped about a blank or core, a method termed xe2x80x9ctraverse windingxe2x80x9d has been used in which the winding position of the tape is traversed back and forth axially of the blank or core. Although traverse-winding permits a greater amount of tape to be wound about the blank or core than in a single spiral wound package, the end portions of the package of tape are prone to telescoping or collapse. This problem is known as xe2x80x9cedge drop-off.xe2x80x9d In addition, for certain tape materials having a high memory (i.e., those tape materials that tend to retain the shape in which they are wound about the blank or core), traverse winding can impart a lasting shape to the tape material that may interfere with its intended use.
U.S. Pat. Nos. Re 32,608, 4,568,033 and 4,603,817 to O""Connor are directed to a package of tape and method and apparatus for making a package of tape that overcome some of the above-mentioned problems. For example, in Re 32,608 and 4,603,817, a plurality of turns of tape are spirally wound in a fixed position without any traversal before proceeding to a next position spaced axially of the core. The package of tape so formed includes a number of body portions of tape formed from between 2 and 10 spirally wrapped turns of tape that are adjoined to one another by a helical traverse. The edges of the each of the plurality of spirally wrapped turns of tape of each of the body portions lie between the same pair of radial planes spaced axially of the package body. As each of the body portions of the package of tape are built up in a series of steps, such a package of tape is termed a xe2x80x9cstep-woundxe2x80x9d package of tape.
In U.S. Pat. No. 4,568,033, each end position of the package of tape includes a plurality of spirally wrapped turns of tape that are formed in a series of steps. However, the interior region of the package is formed from overlapping traversals back and forth between the end positions to fill in the interior region. When the interior portion of the package attains the height of the end positions, the process is repeated.
According to one embodiment of the present invention, a package of tape wound about a cylindrical core is provided. The package of tape comprises a plurality of cylindrical body portions spaced apart along a length of the core, each respective body portion of the plurality of body portions including a plurality of turns of tape. Edges of each of the plurality of turns of tape in each respective body portions are aligned within a respective pair of radial planes spaced apart along the length of the core and within each respective body portion, each approximately full turn of tape of the plurality of turns of tape is offset from an immediately adjacent approximately full turn of tape by a fraction of a width of the tape.
According to another embodiment of the present invention, a package of tape wound about a cylindrical core is provided that comprises a plurality of cylindrical body portions space apart along a length of the core. Each respective body portion of the plurality of body portions includes a plurality of turns of tape. Edges of each of the plurality of turns of tape in each respective body portion are aligned within a respective pair of radial planes spaced apart along the length of the core. Within each respective body portion, a portion of each respective turn of tape of the plurality of turns of tape is offset from an immediately adjacent portion of the respective turn of tape by a fraction of a width of the tape.
According to another embodiment of the present invention, a package of tape wound about a cylindrical core is provided. The package of tape comprises a plurality of cylindrical body portions spaced apart along a length of the core, each respective body portion of the plurality of body portions including a first plurality of turns of tape. Edges of each successive turn of tape of the first plurality of turns of tape in each respective body portion are offset by a fraction of a width of the tape from edges of an immediately prior turn of tape in a first direction. Each respective body portion of the plurality of body portions further includes a second plurality of turns of tape overlying the first plurality of turns of tape, edges of each successive turn of tape of the second plurality of turns of tape in each respective body portion being offset from edges of an immediately prior turn of tape in a second direction that is opposite the first direction.
According to another aspect of the present invention, a method of building a package of tape is provided. The method includes acts of wrapping a first plurality of turns of tape about a cylindrical core at a first position defined by a first pair of radial planes spaced apart along a length of the core so that edges of each approximately full turn of tape of the first plurality of turns of tape are laterally offset from edges of an immediately adjacent turn of tape by a fraction of a width of the tape and within the first pair of radial planes; traversing to a second position defined by a second pair of radial planes spaced apart along the length of the core; and wrapping a second plurality of turns of tape about the cylindrical core at the second position so that edges of each approximately full turn of tape of the second plurality of turns of tape are laterally offset from edges an immediately adjacent turn of tape by the fraction of the width of the tape and within the second pair of radial planes.
According to a further embodiment of the present invention a method of building a package of tape is provided. The method includes acts of wrapping a first plurality of turns of tape about a cylindrical core at a first position defined by a first pair of radial planes spaced apart along a length of the core so that edges of a portion of each respective turn of tape of the first plurality of turns of tape are laterally offset from edges of an immediately adjacent portion of the respective turn of tape by a fraction of a width of the tape and within the first pair of radial planes; traversing to a second position defined by a second pair of radial planes spaced apart along the length of the core; and wrapping a second plurality of turns of tape about the cylindrical core at the second position so that edges of a portion of each respective turn of tape of the second plurality of turns of tape are laterally offset from edges of an immediately adjacent portion of the respective turn of tape by the fraction of the width of the tape and within the second pair of radial planes.
According to yet another embodiment of the present invention, a method of building a package of tape is provided comprising acts of wrapping a first plurality of turns of tape about a cylindrical core at a first position defined by a first pair of radial planes spaced apart along a length of the core so that edges of each successive turn of tape of the first plurality of turns of tape are laterally offset in a first direction by a fraction of a width of the tape from edges of an immediately prior turn of tape and within the first pair of radial planes; traversing to a second position defined by a second pair of radial planes spaced apart along the length of the core, the second pair of radial planes being distinct from the first pair of radial planes; and wrapping a second plurality of turns of tape about the cylindrical core at the second position so that edges of each successive turn of tape of the second plurality of turns of tape are laterally offset in the first direction by the fraction of the width of the tape from edges of an immediately prior turn of tape and within the second pair of radial planes. According to this embodiment, the act of traversing may include an act of wrapping an approximately full turn of tape that contacts one of the edges of each of the first plurality of turns of tape during the act of traversing.
According to the various embodiments of the present invention described herein, a package of tape is provided having firm edge windings that are less susceptible to edge damage than a traditional helical traverse wound package, and in which variations in the offset of adjacent layers in a body portion interlock the layers of tape to improve the stability of the package of tape. With respect to the end position body portions, the interlocking of layers of tape in each end position body portion with layers of tape of an immediately adjacent body portion helps to prevent multiple layers of tape from dropping off, should one of the top-most layers be displaced. This is in contrast to a conventional step wound package of tape in which displacement of a top-most layer of tape of an end position body portion will typically bring underlying layers of tape of the same step along with it. Further, because each of the layers of tape in a step of an end position body portion is interlocked with a layer of tape in an immediately adjacent body portion, a greater number of layers of tape may be wound in a step of the end position body portion before securing those layers of tape to the immediately adjacent body portion by a traversal to the immediately adjacent body portion. This, in turn, can reduce the number of times each end position body portion is visited during winding, further enhancing the stability of the end position body portions, and thus, the package of tape.
Additionally, the slight feathering that is created by variations in the offset of layers of tape in adjacent body portions creates a soft shoulder for the tape material as it traverses from one body portion to an adjacent body portion when the tape is wound and unwound. This minimizes deformation of the tape material and reduces stress to the tape material. It should be appreciated that the heightened stability of each of the body portions, and especially the end position body portions, and the soft shoulder between adjacent body portions permits a greater number of layers of tape to be wound in each body portion. This, in turn, allows formation of a larger diameter package of tape that can include a greater amount of tape than with conventional method of winding.